Wind turbine power generating apparatuses have become increasingly popular in recent years in view of preservation of the global environment. In a typical wind turbine power generating apparatus, pitch angles of blades are variable, and a pitch control is performed in accordance with the operation state of the wind turbine power generating apparatus.
For instance, although not related to a floating-body wind turbine power generating apparatus, Patent Documents 1 to 3 disclose a pitch-control method whereby a load applied to a wind turbine power generating apparatus is reduced. Further, Non-patent Document 1 discloses a method of controlling the pitch of each blade individually so as to reduce an ultimate load of a wind turbine power generating apparatus upon occurrence of gust or shutdown of the system (p. 126-127).